I changed my dash lights over to led’s not so long ago….
The temp and oil gauges had wedge bulb holders…..on my car…so I end up getting these from jaycar for two bucks each
http://www.jaycar.com.au/productView.asp?ID=ZD0390
For the speedo……I ended up cleaning out the glass and guts of the screw in bulb and fitting the wedge led in and soldered it together…….. I just pulled the wire straight and used the soldering iron to melt the end of the led to fit the base of screw bulb.
With a bit of hot melt glue push the whole lot together ….let it set, then just soldered the wires to the base.
They fitted my Australian speedo in length…….but I ended up getting a English speedo with miles and kilometres………which turned out to not as deep as my other one……and the home made bulbs where to long.
I ended up finding some led garden bulbs from bunnings that have around five or six leds in them……..the fit the hole at the back of the speedo perfect….
I just soldered wire from the garden leds to the glass bulb screw base and earthed out the holder with some wire…..
The garden light leds are hpm brand…….and cost twenty dollars for two, they have a white base and a plastic lens thing that pulls off.
I hope this helps
Cheers Neil